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The bandgap modulation and electronic properties modulation of two-dimensional HfSi2N4 monolayer induced by strain, electric field and atomic adsorption are studied by first principles. The HfSi2N4 monolayer was found to be dynamically, thermally, and mechanically stable at equilibrium, and it is a direct semiconductor with a bandgap of 1.87 eV. The bandgap of the HfSi2N4 monolayer can be precisely modulated by strain. Under the action of strain, HfSi2N4 monolayer not only transforms from direct semiconductor to indirect semiconductor, but also improves the absorption of visible light. An external electric field in the 0–0.5 eV/Å range can also modulate the bandgap of HfSi2N4 monolayer from 1.87 eV to 0 eV, and most importantly, at an external electric field of 0.5 eV/Å, HfSi2N4 monolayer shows the characteristics of spin gapless semiconductor. The calculated adsorption energy shows that the structures of H, O and F atoms adsorbed by HfSi2N4 monolayer can all exist stably. The bandgap of the configuration after adsorption of O and F atoms is significantly reduced compared with that of HfSi2N4 monolayer. Furthermore, the HfSi2N4 monolayer after adsorption of H and F atoms is transformed into a magnetic semiconductor. Method: All calculations were performed using Vienna ab initial simulation package, The electronic structure, mechanical properties, electronic properties and other properties were carried out using generalized gradient approximation (GGA-PBE), supplemented by HSE06 and GGA + U. The total-energy and force convergence are less than 10–6 eV and 0.001 eV/Å, respectively. The vacuum on the z-axis is selected 20 Å. The vdW interactions were corrected using the Grimme scheme (DFT-D3). [ABSTRACT FROM AUTHOR]

The mitigation of water flooding in the gas diffusion layer (GDL) at relatively high current densities is indispensable for enhancing the performance of proton exchange membrane fuel cells (PEMFCs). In this paper, a 2D multicomponent LBM model is developed to investigate the effects of porosity distribution and compression on the liquid water dynamic behaviors and distribution. The results suggest that adopting the gradient GDL structure with increasing porosity along the thickness direction significantly reduces the breakthrough time and steady–state total water saturation inside the GDL. Moreover, the positive gradient structure reaches the highest breakthrough time and water saturation at 10% compression ratio (CR) when the GDL is compressed, and the corresponding values decrease with further increase of the CR. Considering the breakthrough time, total water saturation and water distribution at the entrance of the GDL at the same time, the gradient structure with continuously increasing porosity can perform better water management capacity at 30% CR. This paper is useful for understanding the two–phase process in a gradient GDL structure and provides guidance for future design and manufacturing. [ABSTRACT FROM AUTHOR]

With the development of carbon-based electronics, the polycrystalline diamond has drawn much attention in diamond electronic devices; as compared to single crystalline diamond, the scale of the polycrystalline diamond can be fabricated over 4 in. much more easily. However, until now, the influence factors on the surface conductivity of hydrogen-terminated polycrystalline diamond (H-PCD) are still unclear. In this work, the carrier concentration and mobility of H-PCD were investigated through Hall effect measurement. It was found that besides surface roughness, the temperature at which the equilibrium states of adsorption and desorption of H-PCD surface adsorbates are established also plays an important role in carrier concentration and mobility. With the increase of the establishment temperature, both carrier concentration and mobility show a decreasing tendency, which may be determined by the coefficient of the surface ionic scattering, phonon scattering, and the grain boundaries on the H-PCD surface. The investigation of this work will give some insight into the control of the surface conductivity on H-PCD from the aspect of the equilibrium state established temperature and surface roughness. [ABSTRACT FROM AUTHOR]

The chelating ligands of boric acid and amino trimethyl phosphonate prepared a novel flame retardant (BAP) for the cotton fabric. A stable chemical and coordination bond was formed on the surface of the cotton fibers by a simple three‐curing finishing process to make the fabric exhibits excellent durable flame retardancy. Cotton fabrics' tensile strength and whiteness got substantially retained after BAP treatment. 90 g/L BAP‐treated samples (3 curing times, 50 laundry cycles) showed good flame retardancy and durability, holding the largest limit oxygen index, 29.7%, and the shortest damage length, 61 mm. A condensed phase and gas phase synergistic flame retardant mechanism was concluded by thermogravimetric, cone calorimeter tests, and thermogravimetric infrared analysis. [ABSTRACT FROM AUTHOR]

Micro-cracks commonly occur on the catalyst layers (CLs) during the manufacturing of catalyst coated membranes (CCMs). However, the crack shape parameters effect on CLs in-plane (IP) electronic conductivity λ s is not clear. In this work, the relationship between crack parameters and the λ s is obtained based on the two-dimensional (2D) multiple-relaxation time (MRT) lattice Boltzmann method (LBM). The LBM numerical model is validated by the normalized λ s experiment applied on three different home-made cracked CLs, and the parameter study focus on crack width, length, quantity and phase angle are carried out. The results show that the decrease of λ s has different sensitivity | k | to the parameters above. The crack width has little effect on λ s decrease, and the | k w | is 0.038. However, crack arm length and quantity show more significant impact, which | k l | and | k N | are 0.753 and 0.725, respectively. The CLs with different crack propagation directions show significant anisotropy on λ s , and a 53.53% decrease in λ s is observed between 0° and 90° crack phase angle change. To manufacture a high electronic conductivity CL, crack initiation and migration mitigation are highly encouraged. • Crack parameters are defined in the catalyst layer for the first time. • A homemade cracked domain reconstruction method is proposed. • In-plane conductivity is investigated using the 2D MRT lattice Boltzmann method. • Crack length and quantity show a more significant influence than crack width on in-plane conductivity. [ABSTRACT FROM AUTHOR]

Human–machine interaction will be revolutionarily different in the future Internet of Things (IoT) environments. Many displays will be adopted onto electronic devices to enhance human–device communication, even under a very bright sunlight ambience. Thus, power consumption and sunlight visibility are important attributes for this application. Electrophoretic displays (EPDs) have the inherent advantages of ultra‐low power consumption and high sunlight visibility, which are perfectly suitable for IoT applications. The low power consumption resulted from the balance of viscosity, gravity, and other complicated forces involved in the electrophoretic dispersion. This force balance is generally termed "bistability," meaning the particle‐packing can be stable without external power at black and white image states. However, good bistability implies a slow image updating rate, significantly degrades users' experience. In this work, a 3D network structure that undergoes disruption and reorganization with the particles' movement is utilized in the electrophoretic ink dispersion. Dynamic viscosity modulation enables the bistable and fast‐response dual‐working modes. The newly developed design can increase the response speed of EPDs by a factor of 2.38, simultaneously maintaining the bistability. The electronic ink with this reversible network provides a promising solution for the future video‐rate e‐paper displays. [ABSTRACT FROM AUTHOR]

Regulated multi-stage turbocharging is a key technology to achieve energy conservation and CO 2 emission reduction in internal combustion engine with carbon-free fuel. The understanding of performance of the turbocharging system at the engine conditions is essential for the optimization of engine performance. This paper studies unsteady aerodynamic interaction in regulated two-stage turbocharger turbines at pulsating conditions produced by a heavy-duty diesel engine. Results show that the performance of high-pressure turbine (HPT) is highly sensitive to the unsteady stage-interaction, which is profoundly different from that of the low-pressure turbine (LPT). Specifically, when the bypass valve is opened, the cycle-average efficiency of the HPT declines significantly up to 10.8 % compared with that of closed valve. On the other hand, LPT is slightly influenced by the valve state, and the cycle-average efficiency drops by about 0.2 % when the valve is open. The entropy generation method is used to analyze the unsteady loss in HPT and LPT to unveil the mechanism of the unsteady interaction. Detailed flow analysis shows that the swirling flow result in the evident increase of entropy generation in the HPT and LPT volute. Meanwhile, tip leakage loss and incidence loss of HPT is enhanced by unsteady stage interaction. • Influence of unsteady stage interaction on loss generation in two-stage radial turbines at pulsation is firstly studied. • Influence of pulsating condition and status of bypass valve on performance of HPT and LPT are profoundly different. • Unsteady performance of HPT deteriorates dramatically compared to steady state when valve opens. • Significant loss in HPT with open-valve is resulted from both inlet swirl of volute and stronger tip leakage flow in rotor. [ABSTRACT FROM AUTHOR]

[Display omitted] • The temperature sensitivity analysis in different degradation levels is conducted. • An adaptive state-of-health transient thermal model of fuel cells is proposed. • The relationship among the load, health state, and optimal temperature is revealed. To obtain the temperature sensitivity characteristics of the proton exchange membrane fuel cell under different degradation levels, accelerated durability tests and temperature sensitivity tests of the fuel cell are first performed, and the temperature characteristics under different degradation states are analyzed by electrochemical impedance spectroscopy and polarization curve. Besides, an adaptive state-of-health transient thermal model of fuel cells is developed to investigate the effect of operating temperature on the internal gas concentration and hydrothermal distribution characteristics of the fuel cell from a mechanistic perspective. The experimental results of temperature sensitivity validate that the adaptive state-of-health transient thermal model can effectively monitor the steady and transient performance of the fuel cell. Subsequently, a mathematical model is proposed to describe the relationship among the load current, state of health, and optimal temperature using the temperature sensitivity test data and the transient thermal model of the adaptive state of health, which provides important insights into the optimal temperature range tailored to the current state of health of fuel cells to ensure efficient and stable operation of fuel cells all the time and contributes to the fine design of an optimal degradation adaptive temperature control strategy. [ABSTRACT FROM AUTHOR]

The terahertz stealth and shielding performance of a new type of two-dimensional material, borophene, has been studied theoretically and experimentally. Studies have shown that borophene materials have good terahertz stealth and shielding properties. First-principles calculations show that compared with single-layer borophene, few-layer borophene has good terahertz stealth and shielding performance in the range of 0.1~2.7 THz. In the range of 2~4 layers, the terahertz stealth and shielding performance of few-layer borophene increases with the increase of the number of layers. The finite element simulation calculation results also confirmed this point. Using the few-layer borophene prepared by our research group as a raw material, a PDMS composite was prepared to verify the terahertz stealth and shielding performance of the few-layer borophene. In the ultra-wide frequency range of 0.1~2.7 THz, the electromagnetic shielding effectiveness (EMI SE) of the PDMS material mixed with few-layer borophene can reach 50 dB, and the reflection loss (RL) can reach 35 dB. With the concentration of few-layer borophene increasing, the terahertz stealth and shielding effectiveness of the material is enhanced. In addition, the simultaneous mixing of few-layer borophene and few-layer graphene will make the material exhibit better terahertz stealth and shielding performance compared with mixing separately. [ABSTRACT FROM AUTHOR]

Fourier ptychography imaging is a powerful phase retrieval method that can be used to realize super-resolution. In this study, we establish a mathematical model of long-distance camera scanning based on reflective Fourier ptychography imaging. In order to guarantee the effective recovery of a high-resolution image in the experiment, we analyze the influence of laser coherence in different modes and the surface properties of diverse materials for diffused targets. For the analysis, we choose a single-mode fiber laser as the illumination source and metal materials with high diffused reflectivity as the experimental targets to ensure the validity of the experimental results. Based on the above, we emulate camera scanning with a single camera attached to an X-Y translation stage, and an experimental system with a working distance of 3310 mm is used as an example to image a fifty-cent coin. We also perform speckle analysis for rough targets and calculate the average speckle size using a normalized autocorrelation function in different positions. The method of calculating the average speckle size for everyday objects provides the premise for subsequent research on image quality evaluation; meanwhile, the coherence of the light field and the targets with high reflectivity under this experiment provide an application direction for the further development of the technique, such as computer vision, surveillance and remote sensing. [ABSTRACT FROM AUTHOR]

Incorporating two-dimensional graphene sheets, known for their high in-plane thermal conductivity, into silica aerogel enhances both the thermal insulation and mechanical properties of the composite. This work delves into the impact of graphene doping on the solid thermal conductivity of silica composites and their mechanical characteristics, employing molecular dynamics simulations that encompass both amorphous silica bulk and porous silica aerogel structures. Our findings reveal that graphene–silica interface thermal resistance notably restricts heat conduction in graphene doped silica aerogel, with the most pronounced effect occurring when graphene aligns vertically with the heat flux. Within porous silica aerogel, graphene serves as a "heat node", bridging and connecting adjacent pores. A notable "trade-off" emerges: high weight percentages of graphene sheets augment heat transfer through the "heat node effect", whereas the interfacial thermal resistance between graphene and aerogel reduces solid heat transfer, leading to decreased thermal conductivity. Additionally, while the inclusion of graphene sheets offers limited mechanical property enhancements, their two-dimensional structure can cause detachment and slipping from the silica matrix, leading to localized improvements in mechanical strength. This work sets the stage for advancing graphene-based aerogel composites characterized by low thermal conductivity and enhanced mechanical properties. [Display omitted] • Graphene sheet with low doped fraction acts as a thermal resistance in the aerogel composites. • Graphene sheets form the heat node to enhance the thermal conduction, when doped fraction larger than 10%. • The silica–graphene contract atom identification method is proposed. • Limited enhancement in mechanical properties of aerogel composite by doping graphene is found. [ABSTRACT FROM AUTHOR]

In the quest for advanced energy-efficient materials, a reversible adsorption process of water on nanoparticles presents a promising avenue for enhancing the thermal insulation and absorption capabilities of nanoparticle-based materials. Molecular dynamics simulation is carried out to elucidate the intricate water absorption dynamics at the nanoscale. Nanoparticles featuring subpore structures – rather than the conventional ideal spherical models – are utilized to investigate water absorption behavior. Our findings delineate absorption mechanisms – surface adsorption (M g / M 0 of 1.00 with specific area of 632.5 m 2 / g), transition (M g / M 0 of 0.75 with specific area of 897.0 m 2 / g), and penetration (M g / M 0 of 0.59 and 0.47, with specific area of 1003.0 and 1160.0 m 2 / g , respectively) – underscoring the critical role of subpore configurations in modulating these processes. Notably, an optimal nanoparticle structural parameter is identified, optimizing the balance between water adsorption capacity and thermal insulation properties. We unveil a novel mediating effect of subpores that significantly counters the formation of water bridges between nanoparticles – an inevitability in nanoporous materials – thus bolstering material stability and performance. The insights gained from this study shed light on the fundamental mechanisms governing water-nanoparticle interactions. • Water absorption on nanoparticles with subpores at atomic-level within 20 ns are carried out. • Subpores of nanoparticles are found to be able to change water bridge formation. • Identification method of absorbed water molecules at atomic-level is developed. • An optimal nanoparticle structure for silica-nanoparticle based material is found. [ABSTRACT FROM AUTHOR]

Gas absorption capability of material proposes a dominant role in the energy storage, selective gas absorption/capture. Aerogels with ultra-high porosity, ultra-low thermal conductivity have been widely used in gas absorption. However, a persistent limitation of these materials is their static and unalterable gas absorption capacity. In this work, a wrinkled graphene structure is proposed to adjust the gas capability. A series of molecular dynamics (MD) simulations are carried out to propose an atomic-level understanding of the effects of wrinkled structure, including effects of pressure, surface wettability, number of gas molecules, thermal insulation, and mechanical properties. It is found that the gas capability can be reduced by 20% with wrinkle structure. Notably, the linear response between pressure and gas absorption capability is observed. Moreover, wrinkle structure functions as a thermal resistance to restrict solid heat transfer. The mechanical property of the aerogel composite is improved by a doped graphene sheet with a high wrinkle degree. This work will pave the way for the development of aerogel with high and selective gas absorption capability. • MD model of wrinkled graphene doped silica aerogel is built. • A linear response between pressure and gas absorption capability is found. • Wrinkle graphene damages the gas absorption. • High degree of wrinkle graphene improves the mechanical properties. [ABSTRACT FROM AUTHOR]

CO 2 huff- n -puff is a promising method for enhancing oil recovery in tight reservoirs while simultaneously contributing to CO 2 geological storage. However, the performance of this method is significantly affected by fractures resulting from hydraulic fracturing and natural fractures. The impact of fracture on oil transport behavior in different pores remains unclear and warrants further investigation. In this study, CO 2 huff- n -puff experiments were conducted under induced fracture conditions. A new method for quantifying the relationship between transverse relaxation time T 2 and pore radius was proposed by fitting the slopes of the T 2 spectrum and the pore size distribution (PSD) curve derived from Micro X-ray computed tomography (Micro-CT). The impact of the fracture on the effective utilization limit was explored, and the fractal dimensions of different cycles were evaluated during CO 2 huff- n -puff. The results showed that the oil recoveries of the fracture-free and the fractured samples were 19.97% and 31.16%, corresponding to the effective utilization limits of 1.52 μm and 0.96 μm, respectively. Moreover, based on the fractal characteristics of the whole process of CO 2 huff- n -puff, the pore system was divided into micropores (<0.20 μm), small pores (0.20–0.63 μm), intermediate pores (0.63–2.00 μm), and large pores (>2.00 μm). Furthermore, the incremental recovery for each cycle mainly comes from large pores and gradually decreases as the fractal dimension is less than 2.85. The fracture has a significant impact on the migration characteristics of crude oil. The incremental oil in the intermediate pores of the fractured sample, caused by negative convection, was 2.88 times greater than that of the fracture-free sample. Finally, it was found that the gravity effect was more prominent, significantly affecting the remaining oil distributions in fractured reservoirs. • A novel method to describe the relationship between T 2 and pore radius is proposed. • The effective utilization limit is quantified under fracture conditions. • Dynamic fractal dimension is used to classify the pore system. • Characteristics of negative convection are investigated. • The gravity effect significantly impacts the remaining oil distribution. [ABSTRACT FROM AUTHOR]

Cathode recirculation provides a new solution to the accelerated degradation of proton exchange membrane fuel cells (PEMFCs) due to low humidity and high potential at low load conditions. Analyzing the internal impact mechanisms is basis for a more appropriate use of this technology. This paper presents a systematic investigation of the mechanisms by which key operating parameters of the cathode recirculation, including current density, cathode recirculation ratio, and stoichiometry of the fresh air path, affect the internal and external properties of PEMFCs. The voltage suppression effect and humidification effect under different cathode recirculation strategies are first analyzed. Then, as a novelty, the distribution of relaxation times (DRT) method is used to deconvolve electrochemical impedance spectra and qualitatively resolve the polarization impedance under different strategies. DRT is enabled to separate up to five polarization processes with different time constants and assign them to oxygen diffusion, oxygen reduction reaction and proton transport processes affected by the cathode recirculation. Finally, DRT quantified the change in ohmic impedance due to cathode recirculation and confirmed the effect of external humidity changes. This work provides a more in-depth insight into internal mechanisms of cathode recirculation in PEMFCs, and especially provides a comprehensive theoretical basis for the development of idle controllers for automotive PEMFCs in terms of improved durability. • A systematic study of cathode recirculation on PEMFC under low-load conditions. • The polarization process at various recirculation strategies are identified by DRT. • Cathode circulation has positive prospects in vehicle self-humidifying PEMFC system. [ABSTRACT FROM AUTHOR]

Wide-bandgap semiconductors with high carrier mobility are in great demand for high-power radio-frequency applications. In the past decades, extensive efforts have been devoted to investigating the carrier transport properties of hydrogen-terminated diamond (H-diamond), however, achieving its high hole mobility remains a challenge, thereby limiting the development of diamond electronic devices. Herein, we propose a novel strategy to increase the hole mobility of H-diamond by boron nitride (BN) clusters modifications. Amorphous BN clusters were deposited on high-quality H-diamond surfaces using magnetron sputtering. The modified H-diamond exhibits an ultrahigh hole mobility of 1100 cm2 V−1 s−1, over 10-fold higher than that of H-diamond prior to BN modification. Moreover, the BN-modified H-diamond also exhibits outstanding high-temperature tolerance and excellent thermal stability benefitting from the passivation effect of BN. At 380 K, it still maintains a hole mobility of 385 cm2 V−1 s−1. Even after annealing at 350 K for over 8 h, there are no noticeable variations in its carrier transport properties. The hole mobility enhancing mechanism and the factors influencing carrier transport properties of the BN-modified H-diamond are discussed using first principles calculations analysis. The developed BN-modified H-diamond opens up new possibilities for diamond-based radio-frequency electronic devices operating in challenging temperature environments. [Display omitted] • Ultrahigh hole mobility of 1100 cm2 V−1 s−1 is achieved in H-diamond via boron nitride modifications • The developed H-diamond exhibit outstanding high-temperature tolerance and excellent thermal stability • The hole mobility enhancing mechanism and factors influencing carrier transport properties of boron nitride modified H-diamond are discussed [ABSTRACT FROM AUTHOR]

Water transport through the gas diffusion layer (GDL) is vital to proton exchange membrane fuel cells (PEMFCs), especially under flooding conditions. In this paper, a two-dimensional (2D) lattice Boltzmann method (LBM) is applied to reveal the water dynamic characteristics in GDL, and the computational domain is reconstructed based on the experiment. In-situ experiments, including I–V performance and electrochemical impedance spectroscopy (EIS) tests under flooding conditions, are carried out and analyzed. It is found that the porosity distribution inside the GDL is a crucial factor in water dynamic behavior research. The horizontal liquid water saturation (HS w) under the channel of real GDL (with porosity distribution) at 0.4 relative thickness are 3.2 times, 2.1 times and 3.4 times higher than the ideal GDL (without porosity distribution) in the case of 0.8 mm, 1.2 mm and 2.0 mm, respectively. The numerical simulation and experimental study show that water dynamic characteristics under the rib influence cell performance directly. In our LBM model, the GDL water distribution inconsistency (Var w) under 2.0 mm width rib is 43.1% and 28.0% higher than that under the 0.8 mm and 1.2 mm rib, respectively. With the rib wider from 0.8 mm to 2.0 mm, some parts of cell impedance such as R mt , R ct , and L mt increase 64.22%, 98.89%, and 47.46%, respectively. However, GDL under the channel shows no influence on water transport process. • Liquid water dynamics in GDL are revealed via Lattice Boltzmann method. • The 2D non-uniform GDL model is reconstructed on the basis of experiments. • GDL under the rib influences liquid water dynamic dominantly. • The GDL water distribution inconsistency (Var w) under 2.0 mm width rib shows 50.0% higher than that under the 0.8 mm rib. • Originally find the relationship between liquid water distribution inconsistency and mass transfer impedance. [ABSTRACT FROM AUTHOR]

The in-situ electrochemical oxidation of interlayer expanded vanadium disulfide (VS 2 ·NH 3) into hydrated vanadium oxide (V 2 O 5 ·nH 2 O), delivers highly reversible capacity and improved cycling stability for Zinc ion storage. [Display omitted] • An in-situ electrochemical oxidation strategy for interlayer-expanded VS 2 ·NH 3 is reported. • The VS 2 ·NH 3 cathode shows a highly reversible capacity of 392 mA h g−1 at 1.7 V, superior to other VS 2 -based cathodes in the reported literature. • The efficient oxidation process of the VS 2 ·NH 3 cathode in the first charging and the storage mechanism in the subsequent cycles are investigated. • This work reveals the phase transition mechanism of VS 2 ·NH 3 in large voltage range and offers an advanced tactic to design high performance cathode materials. Metallic vanadium dichalcogenides with high conductivity and large layer spacing are fantastically potential to be cathode candidates for aqueous zinc ion batteries. However, simply reliance on the reversible Zn2+ intercalation/deintercalation process in the layer structure of vanadium dichalcogenides makes it suffer from low specific capacity and limited cycling number. Here we report a facile in-situ electrochemical oxidation strategy to boost the zinc ion storage capacity of interlayer-expanded vanadium disulfide (VS 2 ·NH 3) hollow spheres with satisfying cyclic stability. The hydrated vanadium oxide (V 2 O 5 ·nH 2 O) generated from oxidized VS 2 ·NH 3 , are endowed with reduced nanosheet size and subordinated porous structure, which provides abundant accessible sites and accelerates the zinc ion diffusion process. As a result, the VS 2 ·NH 3 derived cathode after the electrochemical oxidation process delivers a high reversible capacity of 392 mA h g−1 at 0.1 A g−1 and long cyclic stability (110% capacity retention at 3 A g−1 after 2000 cycles). The efficient oxidation process of VS 2 ·NH 3 cathode and the storage mechanism in the subsequent cycles are schematically investigated. This work not only reveals the zinc ion storage mechanism of the oxidized VS 2 ·NH 3 but also sheds light on advanced design for high-performance Zn ion cathode materials. [ABSTRACT FROM AUTHOR]

Purpose: The results showed that the use of a magnetic marker could relatively accurately reflect the fracture pattern inside the rock-like material (RLM). Design/methodology/approach: This study investigated the internal structure and fracture pattern of a fractured RLM. Magnetized iron oxide powder, which was used as a magnetic marker, was mixed with water and glue to form a magnetic slurry, which was subsequently injected into a fractured RLM. After the magnetic slurry completely filled the cracks inside the RLM and became cemented, the distribution and magnitude of the magnetic field inside the RLM were determined using a three-dimensional (3D) magnetic field imaging system. Findings: A model for determining the magnetic field strength was developed using MATLAB. Originality/value: This model of 3D magnetic will further be used as a finite element tool to simulate and image cracks inside the rock. [ABSTRACT FROM AUTHOR]

Seawater electrolysis with clean hydrogen energy has bright prospects due to the abundant reserves of seawater on our planet. However, the highly desirable direct seawater splitting with efficient electrocatalyst is still lacking. Herein, Co‐doped metallic VS2 nanosheets with modulated electronic structures and numerous exposed edges were proposed and evaluated as superior catalysts for hydrogen evolution from seawater. The enlarged number of edges through reducing nanosheet size and enriching sulfur defects by Co doping contribute to numerous active sites exposed, leading to desirable catalytic performances. The Co‐doped VS2 nanosheets with 10 % V substituted by Co exhibit excellent catalytic performance in simulated seawater with an onset potential of 196 mV and possesses long‐term stability without obvious current decay after 12‐h test. Moreover, this sample also delivers lower overpotentials of 234 mV at −10 mA cm−2 in acid media. The study can further broaden the development of vanadium chalcogenides in seawater catalysis. [ABSTRACT FROM AUTHOR]

The main purpose of this investigation is to study the dynamic characteristics of shut-in and restart process in reservoirs with high water cut and strong vertical heterogeneity. The physical model, which includes three layers with low, medium, and high-permeability from top to bottom, was made according to the similarity law. Water drive test, the first restart test, and the second restart test were conducted, respectively. Water cut, oil recovery, and saturation distribution of the remaining oil were obtained during the tests. On this basis, mechanisms of shut-in and restart process of the reservoir were analyzed. It is concluded that appropriate developing plan such as layering mining and cyclic waterflooding should be implemented for developing strong heterogeneity reservoirs. The shut-in and restart tests showed that closing the water-flooded layer is beneficial for enlarging the sweep volume. Besides, water cut of 98% does not mean the economic limits of waterflooding. Under the effect of capillary force and gravitational differentiation, oil and water will redistribute in the formation. The redistribution of the oil and water, the fluctuation of the pressure difference, and the rebuild of the flow path, which produce parts of the bypassed oil, are the main mechanisms of the recovery enhancement by shut-in and restart operation. It should be noted that the shut-in and restart process indeed prolongs the waterflooding development. However, simply replying on the oil and water distribution under static conditions cannot greatly enhance the oil recovery. [ABSTRACT FROM AUTHOR]

In order to fabricate a novel antioxidant nanofiber facial mask, a metal cone modified in-situ electrospinning with precise deposition was employed by utilizing Enteromorpha prolifera polysaccharides (EPPs). The metal cone could control the deposition area to achieve precise fabrication of facial mask on skin. The EPPs exhibited remarkable antioxidant ability, as evidenced by the half-maximal inhibitory concentrations (IC 50) of 1.44 mg/mL and 0.74 mg/mL against DPPH and HO• free radicals, respectively. The antioxidant ability of the facial mask was improved by elevating the electrospinning voltage from 15 kV to 19 kV, due to the improved release capacity of EPPs by 7.09 %. Moreover, the facial mask demonstrated robust skin adhesion and moisture-retaining properties compared with commercial facial mask, which was benefited by the in-situ electrospinning technology. Furthermore, cytotoxicity assay, animal skin irritation test, and ocular irritation test collectively affirmed the safety of the facial mask. Thus, this research introduces a novel in situ electrospinning with precise deposition method and a natural antioxidant additive for preparing facial mask. [ABSTRACT FROM AUTHOR]

Hydrogen isotope gases expelled from nuclear fusion reactors can be purified by a process combining catalytic deoxygenation and cryogenic adsorption (77.4 K). In the present work, a novel purification process design is proposed. The experimental result shows that the oxygen volume fraction of the purified hydrogen isotopes is below 0.1 × 10 − 6 with the nitrogen volume fraction less than 1 × 10 − 6 . And it was discovered that the waste amount of hydrogen isotopes after purification is only 100–300 ppm which occupies just 10–30% of the amount of nitrogen impurity through the theory calculation. Therefore, the impurity content of hydrogen isotopes is removed sufficiently by the combined process and the proposed process for purification of the exhaust gases expelled from nuclear fusion reactors can be used as an alternative to the traditional method. • Impurities are removed in hydrogen isotopes. • Catalytic deoxygenation & cryogenic absorption is combined treating impurities. • DX-30 shows a good adsorption property (77.4 K) for N 2 in hydrogen isotopes. • The hydrogen isotopes loss occupies only 10%–30% of the amount of N 2 impurity. [ABSTRACT FROM AUTHOR]

The two-dimensional hole gas (2DHG) at hydrogen-terminated diamond (H-diamond) surface has been widely used in the development of diamond-based electronics. However, the carrier transport behaviors of 2DHG are still poorly understood due to the difficulty in controlling surface adsorbates on H-diamond. In this work, the temperature dependence of the electrical properties of 2DHG on H-diamond was investigated through Hall effect measurements before and after thermal annealing. The results revealed that the establishment of 2DHG equilibrium state was closely related to surface adsorbates, and temperature-induced thermal desorption of adsorbates would lead to a decrease in carrier concentration and an enhancement of mobility on H-diamond. Based on this observation, the carrier mobility of 2DHG (at 300 K) was improved from 170 to 340 cm2 V−1 s−1 after thermal annealing to 400 K. Moreover, with thermal desorption of adsorbates, the activation energy of conductance exhibited an increasing tendency, and the carrier concentration became more dependent on temperature, which can be well explained by percolation theory. A dynamic equilibrium process was also proposed to illustrate the influence of surface adsorbate on carrier concentration and mobility of 2DHG, which provides a feasible method to regulate carrier mobility and concentration on H-diamond surface. [Display omitted] • Carrier mobility on H-diamond surface at 300 K was improved from original 170 to 340 cm2 V−1 s−1 by thermal annealing. • Carrier concentration of 2DHG on H-diamond surface is one of the important factors affecting mobility. • The establishment of 2DHG equilibrium state is closely related to surface adsorbates and temperature. • The carrier mobility and concentration on H-diamond surface can be tuned by surface adsorbates. [ABSTRACT FROM AUTHOR]

Purpose: To study fracture characteristics of jointed rock masses under blasting load, the RFPA2D analysis software for dynamic fracture of rocks based on the finite element method and statistical damage theory was used. Design/methodology/approach: On this basis, this research simulated the fracture process of rock masses in blasting with different joint geometrical characteristics and mainly analysed the influences of distance from joints to blasting holes, the length of joints, the number of joints and joint angle on fracture of rock masses. Findings: The calculation results show that with the constant increase of the distance from joints to blasting holes, the influences of joints on blasting effects of rock masses gradually reduced. Rock masses with long joints experienced more serious damages than those with short joints. Damages obviously increased with the changing from rock masses without joints to rock masses with joints, and when there were three joints, the further increase of the number of joints had unobvious changes on blasting effects of rock masses. Joints showed significant guidance effect on the propagation of cracks in blasting: promoting propagation of main vertical cracks deflecting to the ends of joints. Originality/value: The research results are expected to provide some theoretical bases in practical application of engineering blasting. [ABSTRACT FROM AUTHOR]

Abstract A novel and highly active vanadium self-intercalated C/V 1.11 S 2 nanosheets with abundant active sites are fabricated by a simple hydrothermal-calcinations method. The structures and morphology of C/V 1.11 S 2 nanosheets were characterized by XRD, SEM, XPS and TEM. Particularly, PVP (polyvinylpyrrolidone) was used as surfactant to control the morphology of vanadium sulfide and carbon source to reduce the vanadium sulfide into vanadium self-intercalated V 1.11 S 2 phase with rich active sites. The C/V 1.11 S 2 nanosheets showed an excellent electrocatalytic activity for hydrogen evolution reaction, including a low onset potential of 15 mV vs. RHE (reversible hydrogen electrode), small Tafel slope of 51 mV dec−1, as well as extraordinary catalytic stability. The first-principle calculations further confirmed that the V 1.11 S 2 has a much lower Gibbs free energy for hydrogen adsorption (ΔG H) than that of VS 2. The enhanced HER performance can be contributed to the unique vanadium self-intercalated structures, nanostructured morphology and rich sulfur defects of the obtained C/V 1.11 S 2 nanosheets. We believe that the C/V 1.11 S 2 can be used as electrocatalyst in chemical engineering industry and our method provides guidance on the fabrication of other defective transition-metal dichalcogenides to improve their catalytic performances. [ABSTRACT FROM AUTHOR]

Abstract This paper investigates performance and loss mechanism of a nozzled twin-entry mix-flow turbine at different admissions. Two sets of partial admissions and unequal admissions are analysed via experimentally validated numerical method. Results show that discrepancies of turbine efficiency between symmetrical unequal admissions (swopping inlet pressure on two entries) increase when unequal admissions approach to partial admissions, although their swallowing capacity is similar. Loss breakdown of turbine shows that loss is higher in nozzle but lower in rotor when the majority of flow is fed from upper part of the component (near shroud). Opposite phenomenon happens when the majority is fed from lower part (near hub). The reason for loss characteristic of nozzle is front-sweep configuration of the nozzle vane which results in evident flow separation when the flow is fed near the shroud. The reason for loss characteristic of rotor is the tornado-shaped vortex when the flow is fed from the hub. The tornado vortex is initiated by large incidence angle near hub and developed by the combination of Coriolis force, pressure gradient and centrifugal force. The study unveils loss mechanism among different admissions for a twin-entry turbine, which may enlighten the design methodology of the turbine with twin-entry volute. Highlights • Admission influence on performance and loss in a twin-entry nozzled mix-flow turbine is firstly understood. • Loss in nozzle and rotor is re-distributed by different admissions. • Configuration of front-sweep vane is root of loss differences in nozzle at different admissions. • Tornado vortex caused by Corio force, pressure gradient and centrifugal force is root of loss differences of rotor. [ABSTRACT FROM AUTHOR]

A novel photocatalyst-free visible-light-mediated dithioacetalization of aldehydes and thiols has been developed. This protocol is operationally simple, mild and atom-economical, which provides an environmental benign access to dithioacetals at room temperature under aerobic conditions. [ABSTRACT FROM AUTHOR]

A biopolymer-chitosan based Supramolecular Hydrogel type solid state Electrolyte (SHE) is prepared via a simple and fast cross-linking between chitosan and Li+/Ag+. The obtained SHE itself shows high thermal stability and excellent flexible and mouldable properties. When integrated in an asymmetric supercapacitor with MnO2 as the positive electrode and active carbon as the negative electrode, it can survive more than 10 000 cycles with the areal capacity of 10 mF cm−2 at the 1.8 mA cm−2 current density. [ABSTRACT FROM AUTHOR]

A centrifugal compressor is operated at unsteady exit conditions in many scenarios. The performance of compressor stability is notably altered by the unsteady conditions, but reasons for the influence have not been understood yet. This paper studies the mechanism of pulsatile backpressure on the stability performance of a centrifugal compressor. Firstly, the aerodynamic stability is discussed in the compressor unit by 3-D unsteady CFD method. A street of vortexes is generated near shroud in the impeller inducer at both constant and pulsating conditions, which is caused by the rolling-up of shear layer between the tip clearance flow and main flow due to K-H instability. But the rolling-up of the shear layer is evidently depressed by the pulsating backpressure. Consequently, the secondary flow and blockage in the impeller are alleviated, and hence the aerodynamic stability of the compressor is benefited. Next, the dynamic stability is studied in the compression system theoretically via Lyapunov function in perspective of energy balance. The results show that both the characteristics of compressor and throttle are influenced by the pulsating condition. Specifically, the characteristic of compressor becomes steeper at pulsating condition and thus less energy is added into the compression system. On the other hand, the characteristic of throttle also becomes steeper, thus the capability of energy-damping in the system deteriorates. The dynamic instability of the system is determined by the trade-off between these two influences. Finally, the route of the influence by the pulsating backpressure on the compressor stability is drawn according to both the aerodynamic instability of the compressor component and dynamic instability of the compression system. [ABSTRACT FROM AUTHOR]

The turbocharger is the key enabler for energy conservation in Internal Combustion Engine (ICE). A turbine of a turbocharger is fed by highly pulsating flow due to the reciprocating engine, resulting in different behavior from that at steady conditions. This paper investigates the behavior of a mix-flow turbine under pulsating conditions via an analytical model and an in-house developed 1-D unsteady code ONDAS . Firstly, an analytical model of the ‘unsteadiness’ based on the mass flow imbalance is built and the mechanism of the unsteady behavior is discussed in details. Next, a 1-D unsteady model of the turbine under pulsating conditions is established and validated by experimental results. Finally, influence of the frequency, the magnitude and their product on unsteady behavior of the turbine is investigated by the reduced order model for further exploration of the analytical model. The investigation clearly demonstrates the impact of pulsating flow on the unsteady performance and unveils the mechanism of the ‘unsteadiness’ of turbine under pulsating conditions. [ABSTRACT FROM AUTHOR]

Engine downsizing is a proven method for CO 2 reduction in Internal Combustion Engine (ICE). A turbocharger, which reclaims the energy from the exhaust gas to boost the intake air, can effectively improve the power density of the engine thus is one of the key enablers to achieve the engine downsizing. Acknowledging its importance, many research efforts have gone into improving a turbocharger performance, which includes turbine volute. The cross-section design of a turbine volute in a turbocharger is usually a compromise between the engine level packaging and desired performance. Thus, it is beneficial to evaluate the effects of cross-sectional shape on a turbine performance. This paper presents experimental and computational investigation of the influence of volute cross-sectional shape on the performance of a radial turbocharger turbine under pulsating conditions. The cross-sectional shape of the baseline volute (denoted as Volute B ) was optimized ( Volute A ) while the annulus distribution of area-to-radius ratio (A/R) for the two volute configurations are kept the same. Experimental results show that the turbine with the optimized volute A has better cycle averaged efficiency under pulsating flow conditions, for different loadings and frequencies. The advantage of performance is influenced by the operational conditions. After the experiment, a validated unsteady computational fluid dynamics (CFD) modeling was employed to investigate the mechanism by which performance differs between the baseline volute and the optimized version. Computational results show a stronger flow distortion in spanwise direction at the rotor inlet with the baseline volute. Furthermore, compared with the optimized volute, the flow distortion is more sensitive to the pulsating flow conditions in the baseline volute. This is due to the different secondary flow pattern in the cross-sections, hence demonstrating a direction for desired volute cross-sectional shape to be used in a turbocharger radial turbine for internal combustion engine. [ABSTRACT FROM AUTHOR]

As an ultra-wide bandgap semiconductor, hexagonal boron nitride (h-BN) has drawn great attention in solar-blind photodetection owing to its wide bandgap and high thermal conductivity. In this work, a metal-semiconductor-metal structural two-dimensional h-BN photodetector was fabricated by using mechanically exfoliated h-BN flakes. The device achieved an ultra-low dark current (16.4 fA), high rejection ratio (R 205nm/ R 280nm = 235) and high detectivity up to 1.28 × 1011 Jones at room temperature. Moreover, due to the wide bandgap and high thermal conductivity, the h-BN photodetector showed good thermal stability up to 300 °C, which is hard to realize for common semiconductor materials. The high detectivity and thermal stability of h-BN photodetector in this work showed the potential applications of h-BN photodetectors working in solar-blind region at high temperature. [ABSTRACT FROM AUTHOR]

Twin-entry radial turbine has an evident advantage of enhancing the output power in internal combustion engine, while it is confronted by complex inlet conditions because of the interval flow feeding into two limbs. Although the performance of twin-entry turbine is notably influenced by admission conditions, detailed flow mechanism is yet fully revealed in previous researches. This paper investigates the mechanism of the influence by different admissions on a nozzleless twin-entry turbine via experimentally validated numerical methods. Turbine performance is studied under different admission conditions and the results demonstrate that twin-entry turbine performance is notably different between two partial admission conditions, although the volute passage is symmetrically divided. Rotor decomposition methods are employed for the analysis of loss distributions to understand this performance difference. Flow separation and tornado vortex generated near the rotor inlet is confirmed as the key source for the flow loss in the rotor. The off-design incidence angle near the hub rather than the shroud is the reason for the vortex initiation in the twin-entry turbine. Moreover, the volute flow features demonstrate that volute leakage flow is the reason for the lower incidence angle near the blocked limb. Consequently, the mechanism of the asymmetric performance of the symmetric twin-entry turbine under partial admission conditions is revealed. [ABSTRACT FROM AUTHOR]

• Aerodynamic interaction between impeller and volute at pulsating backpressure are investigated. • Volute-induce pressure distortions are closely coupled with pulsation and operational conditions. • Distortion magnitude varies in phase with mass flow rate near surge but out of phase near choke. • Influence of pulsation on secondary flow in impeller is discussed via comparison with quasi-steady case. • Vortex street generated in inducer due to K-H instability is drastically depressed by pulsating condition. The performance of a centrifugal compressor is strongly influenced by pulsating backpressure condition, but little knowledge of the mechanism has been obtained. This study investigates aerodynamic interaction between impeller and volute at pulsating condition via experimentally validated numerical method. Results show that the features of volute-induce distortion at impeller exit are closely coupled with pulsating backpressure at different operational conditions. Specifically, the volute-induce pressure distortion varies out-of-phase with the mass flow rate near surge condition (OP2), but in phase near choke condition (OP1). The circumferential flow distortion at the impeller outlet manifests a notably unsteady effect at pulsating conditions for both OP1 and OP2. Comparing with the quasi-steady cases, the magnitude of the distortion is alleviated maximally by 2.3% and 2.7% for OP1 and OP2, respectively. The evolution of secondary flow patterns in the impeller show that an array of vortex tubes appears in the shroud region of the inducer downstream the main blade leading edge. It is resulted from the rolling-up of vortex sheet due to the K-H instability. The pulsating backpressure can profoundly depress the development of the vortex street. Therefore, the blockage effect by the vortex street in the inducer is alleviated. [ABSTRACT FROM AUTHOR]

The intermittent throttling effects of intake valves of internal combustion engine generate pulsations at compressor exit, which has a great impact on the compressor performance. In this paper, the influence of pulsation on the compressor is studied via unsteady 3-D numerical method validated by experiments. Results show that the cycle-average efficiency is lower than the quasi-steady value. The impeller is confirmed as the main reason for efficiency deterioration according to entropy generation analysis, due to the difference of secondary flow patterns. The tip leakage vortex at impeller inlet is alleviated at pulsating condition because of inertia effect, resulting in a lower velocity thus higher incidence angle near splitter. The stronger separation and tip leakage flow at splitter leading edge lead to the wake with higher losses. Moreover, the circumferential distortion at the impeller exit is found to be weaker under pulsation. It is caused by two reasons: the flow field, which is closer to the quasi-steady one with a higher mass flow rate due to the lagging effect; the additional pressure gradient in volute caused by propagation of pulse. It results in an evener flow field and improves impeller stability. Specifically, the recirculation region at impeller inlet shrinks 5% under pulsation. [ABSTRACT FROM AUTHOR]

• A new diffusion model based on the whole process fitting was proposed. • The model consists the process of both depletion and diffusion. • The convection has a significant effect on the molecular diffusion. • Mass and rate fitting charts were used to determine diffusion coefficients. • The model fully describes the dynamic diffusion process and diffusion distance. CO 2 diffusion is of great importance for enhanced oil recovery (EOR), production prediction, and performance forecast of carbon capture and storage (CCS) in shale reservoirs. This work aims to determine the diffusion coefficient of the shale reservoir during CO 2 huff and puff development. Firstly, combining pressure decay experiments and mathematical modeling studies, this paper developed a dynamic method to determine the diffusion coefficients of CO 2 in cores under shale reservoir conditions. Based on Fick's law, MATLAB software was used to build the fitting chart under different diffusion coefficients. The diffusion coefficient was determined by matching experimental data. During the experiment, the reservoir's pore pressure and confining pressure were simulated, and a saturation-depletion-diffusion experiment method was established to simulate the natural reservoir conditions. The effects of different initial pressures on diffusion were compared in pressure decay experiments. The mathematical model of the diffusion coefficient of CO 2 was established, and the fitting chart of diffusion coefficient considering time step was derived. The diffusion distance of different diffusion coefficients and different times was compared. The results show that the diffusion coefficient of CO 2 in shale is between 5*10-8 ~ 5*10-7 cm2/s, and the diffusion rate is 0.28 cm/d under the condition of 20 MPa and 319.55 K. In addition, when the diffusion coefficient increases by one order of magnitude, the diffusion distance increases by 200%. [ABSTRACT FROM AUTHOR]

Abstract: β-MnO2 with semi-tubular morphology has been prepared in a mixed solution of KMnO4 and MnCl2 by a facile hydrothermal route without using templates, catalysts, and organic reagents. The structure of the obtained β-MnO2 is systematically investigated by XRD, SEM, and TEM. Results show that the as-prepared β-MnO2 has novel semi-tubular morphology, and its particle shows a diameter of 300–400nm and length up to 1–4μm. The prepared β-MnO2 shows a good electrochemical performance, and delivers a discharge capacity of 195mAhg−1 after 40 cycles between voltage limit of 1.5 and 4.5V at a constant current density of 20mAg−1. [Copyright &y& Elsevier]

Abstract: Hollow MnO2 spheres were successfully prepared via a simple hydrothermal method at 150°C within 20min, without assistance of any templates or surfactants, just by appending Fe3+ ions to a mixed system of KMnO4 and MnSO4. The obtained samples were systemically characterized by XRD, SEM, TEM, N2 adsorption–desorption and element analyses. Results show that the MnO2 sample has hierarchical hollow sphere morphology and the hollow sphere is consisted of nanorods. A possible growth mechanism of hollow MnO2 spheres is proposed on the basis of the experimental results. Fe3+ ions are found to be crucial in controlling the growth of hollow MnO2 spheres. The electrochemical performance indicates that the synthesized hollow MnO2 spheres show an ideal capacitive behavior and good cycling stability at a sweep rate of 10mVs−1 in a Na2SO4 solution. The specific capacitance of the samples by adding Fe3+ ion is found to be three times higher than the samples without adding iron ion. [Copyright &y& Elsevier]

High cycle fatigue (HCF) of radial turbine blades is one of key issues of turbochargers and it determines the reliability of the device. Most of researches about HCF of radial turbine blades focus on vaned turbines, whereas few investigations have been carried out on vaneless turbines which are widely applied in automobile turbochargers. This paper studies the blade vibration mechanism of a vaneless radial turbine at low excitation order via one-way fluid–structure interaction simulation method validated by experiments. The results surprisingly demonstrate that blade vibration response does not increase consistently with turbine load. Instead, a non-monotonic correlation is observed between vibration response and turbine load. The energy analysis is employed to understand the phenomenon and the results manifest that the variation of energy imposed on blade suction surface is the direct reason for the non-monotonic correlation. Detailed flow field analysis further suggests that the non-monotonic trend of energy on suction surface is caused by the interaction of two flow structures at different turbine loads: separation vortex at blade leading edge and tip leakage vortex caused by pressure difference between pressure surface/suction surface. The study of blade excitation in this research can enlighten the new design of vaneless turbine with both good performance and high reliability. • Vibration response VS turbine load of a vaneless radial turbine is studied by FSI. • 'V-shape' correlation between vibration response and turbine load is firstly observed. • Energy analysis indicates that variation of energy on SS results in 'V-shape'. • Interaction between separation vortex and tip leakage leads to high response at low load. • Strong flow distortion induced by volute tongue leads to high response at high load. [ABSTRACT FROM AUTHOR]

In recent years, we have witnessed numerous indoor fires caused by the flammable properties of cotton. Flame-retardant cotton deserves our attention. A novel boric acid and diethylenetriaminepenta (methylene-phosphonic acid) (DTPMPA) ammonium salt-based chelating coordination flame retardant (BDA) was successfully prepared for cotton fabrics, and a related retardant mechanism with ion transfer was investigated. BDA can form a stable chemical and coordination bond on the surface of cotton fibers by a simple three-curing finishing process. The limiting oxygen index (LOI) value of BDA-90 increased to 36.1%, and the LOI value of cotton fabric became 30.3% after 50 laundering cycles (LCs) and exhibited excellent durable flame retardancy. Fourier-transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) methods were used to observe the bonding mode and morphology of BDA on cotton fibers. A synergistic flame-retardant mechanism of condensed and gas phases was concluded from thermogravimetry (TG), cone calorimeter tests, and TG-FTIR. The test results of whiteness and tensile strength showed that the physical properties of BDA-treated cotton fabric were well maintained. [ABSTRACT FROM AUTHOR]

Raising the cutoff voltage can efficiently increase the energy density of lithium cobalt oxide (LCO). However, upon charging over 4.55 V the LCO undergoes irreversible phase transition from the pristine O3 phase to the metastable H1‐3 phases, causing serious side reactions, which results in poor cycling stability. Herein, a multifunctional aqueous composite binder derived from the cross‐linking of fucoidan (FUC) and polyacrylamide (PAM) is developed to enhance the stability of LCO cathode at 4.6 V. The cross‐linking interaction of FUC and PAM provides a uniform coating on the surface of LCO and ensures a high peel strength for the electrode, effectively mitigating irreversible phase transition and detrimental interface side reactions. More importantly, the sulfur ester and amide groups of FUC‐PAM favorably function as surface charge compensators to the high valent Co upon charging under high voltages, thus stabilizes the surface lattice of LCO and suppresses the detrimental oxygen release. As expected, the LCO with a cutoff voltage of 4.6 V exhibits a high capacity retention of 90% after 100 cycles at a current density of 110 mA g−1. The interfacial coordination effect of composite binders offers a novel strategy to enhance the stability of high‐voltage LCO for high‐energy lithium‐ion batteries. [ABSTRACT FROM AUTHOR]

Keywords: Co-doped VS2; edge activity; electronic structure; hydrogen evolution reaction; seawater electrolysis EN Co-doped VS2 edge activity electronic structure hydrogen evolution reaction seawater electrolysis 2093 2093 1 05/10/21 20210507 NES 210507 B The Front Cover b shows that cobalt-doped metallic vanadium disulfide nanosheets exhibit excellent catalytic performance for hydrogen evolution reaction of seawater electrolysis. Co-doped VS2, edge activity, electronic structure, hydrogen evolution reaction, seawater electrolysis. [Extracted from the article]

This paper investigates turbine performance and gasdynamic behaviours of a radial turbine confronted by pulsating inflow via detailed flow measurement. Firstly, pressure propagation in the volute over circumferential direction is captured by six pressure transducers. The propagation speed is confirmed to be the sum of bulk flow velocity and sonic velocity by the experiment. Local flow parameters also propagate at the same speed with pressure pulse, which indicates that pulsations of the flow parameters are driven by the pulse of pressure. An evident phase-shift is observed between input power and output work, which is mainly resulted from the pulse propagation in the inlet duct. Furthermore, the pressure pulse at rotor inlet is evidently out-of-phase with that at rotor exit, producing a larger hysteresis loop of swallowing capacity. Specifically, the cycle-averaged input work is about 22.2% higher than the case with constant exit pressure. It is found to be resulted from the phase-flip of the pulse at rotor exit due to the gasdynamic behaviour at the interface between the rotor and exit duct, where sudden expansion happens. This paper unveils the gasdynamic behaviours of turbine confronted by pulsating inflow and can have a guide effect for performance enhancement design methodology. • Gasdynamic behaviours of turbine exposed to pulsating flow are experimentally and numerically studied. • Pressure, temperature and mass flow propagate at same speed of sonic speed puls flow velocity. • Phase shift between input/output power results from pulse propagation in inletduct and volute. • Pulse phase-flip in rotor leads to 23.4% wider range of pressure ratio and 22.2% higher power. • Pulse phase-flip at trailing edge resluts from gasdynamic behaviours of sudden expansion. [ABSTRACT FROM AUTHOR]

Centrifugal compressor is confronted by pulsating backpressure when coupled with turbocharged internal combustion engine. Few studies have been reported on the understanding of pulsating flow field in the compressor although its performance is notably influenced by the strongly pulsating condition. This paper experimentally studies unsteady flow field in a centrifugal compressor at pulsating backpressure conditions. Experimental facilities and methodology are introduced firstly, followed by detailed discussions on experimental results of unsteady flow at different pulsating conditions. Results show that the pulses of pressure and mass flow rate are alleviated as the pulses propagate from compressor exit to the impeller, but then are enhanced remarkably in the impeller inducer. Flow field at compressor inlet manifests that the axial velocity and the incidence angle are evidently distorted in both circumferential and radial directions induced by the volute at both steady and pulsating conditions. Specifically, the incidence angle is higher in the region upstream the volute tongue than the values downstream the configuration. The patterns of distortions vary periodically with the pulsating backpressure. In particular, comparing with the variation near hub region, the incidence angle varies with the magnitude as about 10 degrees near 85% blade height, implying that the flow in spanwise direction responses to the pulsating backpressure with different sensitivity. The study experimentally demonstrates the clear evidence of the unsteadiness of the flow field in the compressor at pulsating backpressure conditions. [ABSTRACT FROM AUTHOR]

Turbine with twin-entry volute has advantage of utilising energy from pulsatile exhaust gas and improving low-speed torque of an internal combustion engine. This paper investigates unsteady performance of a mixed flow turbine with nozzled twin-entry volute confronted by pulsatile incoming flow. The turbine performance at pulsating conditions with different Strouhal numbers (St) is studied via experimentally validated numerical method. Results show that the unsteadiness of turbine performance is enhanced as Strouhal number increases. In particular, the cycle-average efficiency at St = 0.522 is about 3.4% higher than that of quasi-steady condition (St = 0). Instantaneous loss breakdown of the turbine shows that the entropy generation rate of turbine components reduces evidently at pulsating conditions as Strouhal number increases, especially for the nozzle. Specifically, the cycle-averaged reduction of the loss in the nozzle is 37.3% at St = 0.522 compared with that of St = 0. The flow analysis shows that secondary flow which contributes to the majority of loss in the nozzle, including flow separation, horseshoe vortex, and reversed flow near the leading edge, are notably alleviated as Strouhal number increases. The alleviation of the flow structures are resulted from two reasons: one is that the flow distortion at the nozzle inlet is evidently depressed by the pulsating conditions, the other is that the inertia of the low momentum flow in the nozzle damps flow evolution at pulsating incoming flow. Consequently, the loss is reduced and the turbine performance is benefited by the pulsating inflows. [ABSTRACT FROM AUTHOR]

Pressure fluctuations in intake manifold of Internal Combustion Engine introduce a pulsating boundary condition to the centrifugal compressor. In this study, the performance of centrifugal compressor exposed to pulsating backpressure is experimentally investigated. Unsteady performance and surge characteristic of the compressor at different pulsating conditions are analyzed. Results show that instantaneous performance of the compressor forms a hysteresis loop encapsulating steady performance. A correlation of compressor unsteadiness with pulse frequency, magnitude, and local slope of the characteristic curve is obtained based on measurements. The results show that cycle-average performance of the compressor is notably lower than that at constant conditions. Specifically, the averaged peak efficiency at pulsating condition drops by 3%–7%. Moreover, Fast Fourier Transformation method is applied to study surge characteristics at pulsating conditions. Results manifest that compressor surge is postponed remarkably by pulsating backpressure at the three speeds. As the compressor approaches to small mass flow rate, flow fluctuations decay quickly and then increase dramatically when the surge happens. This phenomenon is resulted from the influence of the slope of characteristic curve on the filling-empty effect and compressor stability. Larger slope produces weaker filling-empty effect and hence smaller size of the loop, but reduces the stability of compressing system and triggers compressor surge. [ABSTRACT FROM AUTHOR]

The nitrogen-vacancy (NV) color center in chemical vapor deposition (CVD) diamond has been widely investigated in quantum information and quantum biosensors due to its excellent photon emission stability and long spin coherence time. However, the temperature dependence of the energy level of NV color centers in diamond is different from other semiconductors with the same diamond cubic structure for the high Debye temperature and very small thermal expansion coefficient of diamond. In this work, a diamond sensor for temperature measurement with high precision was fabricated based on the investigation of the energy level shifts of NV centers by Raman and photoluminescence (PL) spectra. The results show that the intensity and linewidth of the zero-phonon line of NV centers highly depend on the environmental temperature, and the energy level shifts of NV centers in diamond follow the modified Varshni model very well, a model which is better than the traditional version. Accordingly, the NV color center shows the ability in temperature measurement with a high accuracy of up to 98%. The high dependence of NV centers on environmental temperature shows the possibility of temperature monitoring of NV center-based quantum sensors in biosystems. [ABSTRACT FROM AUTHOR]

Solar-blind ultraviolet imaging detector is widely applied in many commercial and military fields, such as missile warning, guidance, ultraviolet communication, biomedical analysis, and police reconnaissance. High-performance pixel photodetector is the core of imaging technology. Therefore, its construction attracts intensive attentions in recent years. In this work, 8 × 8 planar pixels were constructed on high quality single crystal diamond using ultraviolet direct writing lithography. A typical pixel photodetector in metal-semiconductor-metal (MSM) structure achieved outstanding photo-response properties of a low dark current of 10−13–10−12 A at 50 V, a high light-dark current switching ratio over 105), a high responsivity of 22.6 A/W, and a decent specific detectivity of 4.2 × 1014 Jones. Moreover, the detector has a fast response time of 13 ns. Additional optoelectronic studies demonstrate the strong homogeneity and repeatability of the photodetectors array, enabling it to serve as a reliable solar-blind imaging photodetector with high spatial resolution. [Display omitted] • Multiple pixel units with homogeneity can be fabricated by direct writing without mask on high-quality diamond grown by homoepitaxy. • The single crystalline diamond photodetector array presents nanosecond rise time for solar-blind imaging. • High-fidelity imaging can be realized by employing the single crystal diamond photodetectors as sensing pixels. [ABSTRACT FROM AUTHOR]